THE CONTROL OF TfiE RESPIRATION 



365 



in the expired air from that in the alveolar air is greater in relatively small expira- 

 tions. If more exact work is desired, the O content can be determined on each 

 specimen, the respiratory quotient calculated, and only those expirations which show 

 the same respiratory quotient combined. 



In the table each observation is compared with each of the others in all possible 

 combinations. 



General average for CO2 in alveolar air, 5.13. 



General average for dead space, 172: Dead space in valves in this experiment was 

 about 30 c.c. 



Another method which has been suggested for clinical purposes is that of Plesch; this 

 consists in having the subject breathe several times in and out of a small bag. It is 

 assumed that after such respiration the composition of the air in the bag will become 

 the same as that in the alveoli. Although this is no doubt true, it has been shown 

 that the method is fallacious, because the CO o tension determined in this way is not 

 that of the arterial blood alone, but is the average between it and that of the venous 

 blood. 



